Recently, a new class of thermoelastic sulfonated polymers has been described in a number of U.S. patents. These sulfonated polymers are derived from polymeric materials having olefinic unsaturation, especially elastomeric polymers such as butyl and EPDM rubbers. U.S. Pat. No. 3,642,728, herein incorporated by reference, clearly teaches a method of selective sulfonation of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer. The olefinic sites of the elastomeric polymer are sulfonated by means of a complex of a sulfur trioxide donor and a Lewis base. The SO.sub.3 H groups of the sulfonated elastomer can be readily neutralized with a basic material to form an ionically cross-linked elastomer at room temperature having substantially improved physical properties over an unsulfonated elastomer. However, these sulfonated elastomers, unlike these sulfonated elastomers may be processed like a conventional thermoplastic at elevated temperatures under a shear force in the presence of selected plasticizers (preferential in their interaction toward the sulfonate moeities) which dissipate the ionic associations at the elevated temperatures thereby creating a reprocessable elastomer.
The basic materials used as neutralizing agents are selected from organic amines or basic materials selected from Groups I, II, III, IV, V, VIB, VIIB and VIII and mixtures thereof of the Periodic Table of Elements.
U.S. Pat. No. 3,836,511, herein incorporated by reference, teaches an improved process for the sulfonation of the olefinic sites of the elastomeric polymer, wherein the improved sulfonating agent is selected from acetyl sulfate, propionyl sulfate and butyryl sulfate. The neutralizing agents employed to neutralize the acid form of the sulfonated elastomeric polymers are organic amines.
U.S. Pat. No. 3,870,841, herein incorporated by reference, teaches a method of plasticization of the polymeric backbone of a neutralized sulfonated plastic polymer by means of a polymer chain plasticizer which is a liquid compound having a boiling point of at least about 120.degree. F. The polymer chain plasticizer is selected from a dialkyl phthalate, a process oil or an organic acid ester. Additionally a domain plasticizer can be incorporated into the composition, wherein the domain plasticizer reversibly disrupts the association of the sulfonate groups at the temperature of forming.
U.S. Pat. No. 3,847,854, herein incorporated by reference, teaches a method of improving the processability of neutralized sulfonated elastomeric polymers by the addition of a preferential plasticizer which has at least one functional constituent which exhibits a bond moment whose absolute value is at least 0.6 Debyes, and must be a liquid at the desired processing temperature of the neutralized sulfonated elastomeric polymer.
These four aforementioned patents are related to sulfonated polymers, wherein the sulfonated polymer is a major portion of the compositions. The present invention relates to the modification of polar thermoplastic resins with a minor portion of a sulfonated polymer in order to improve the glass transition temperature as well as to improve the stiffness and alter the melt processability of the thermoplastic resin.
U.S. Pat. application Ser. Nos. 542,502 and 524,512, of R. D. Lundbert, H. S. Makowski and J. Bock filed on November 18, 1974, describe the blending of a minor portion of a crystalline polyolefinic material with a neutralized sulfonated elastomeric polymer in an attempt to improve both the rheological and physical properties of the elastomeric polymer. The selection of the use of the crystalline polyolefinic material to improve both the stiffness as well as improving the melt viscosity of the composition was based in part upon the limitation of the use of fillers such as carbon black, clays, calcium carbonate or silicates as a single additive to the elastomeric polymer. Although fillers in combination with an elastomeric polymer increase the hardness of the composition, these fillers deteriorate the melt viscosity of the resultant composition. The compositions of these two applications having a major portion of the sulfonated polymer and a minor portion of a non-polar thermoplastic.
The unique and novel compositions of the present invention provide compounds with improved glass temperature and stiffness which was previously unattainable by practicing the teachings of the aforementioned patents and applications. The blend compositions of the present invention solves the problem of improving the glass transition temperature and stiffnes for polyvinyl chloride for use in hot water pipes.
For example, the incorporation of 10 parts per hundred by weight of a neutralized sulfonated EPDM into 100 parts of a polyvinyl chloride resin increases the glass transition temperature by about 14.degree. C., thereby improving the upper service temperature limit of the thermoplastic blend.